My wife and I jointly own all of our MVC weeks.
Due to a historical quirk, I am Primary Owner for some of these my Wife is Primary Owner for others.
We have separate MVC Owner accounts, but we had always managed our Ownership through just one account (mine)
Many years ago now when MVC changed their systems this did cause a temporary problem, needing us to make reservations…etc only from the Primary Owner account.
After several months of hassle, MVC agreed to change our account set up so that once again we could manage all of our Ownership from either account and this continues to be the case thankfully.
We each have our separate Bonvoy numbers associated with our separate Owner accounts.
I am Lifetime Titanium through Marriott stays.
When I reached this level, we requested my Wife’s Bonvoy account to be the one associated with our joint Ownership so that as Chairman’s Club Owners she would also have Titanium level.
This has worked perfectly well ever since.